The invention relates to a device, particularly a router, for cutting a workpiece by means of a tool bit rotatingly driven in working rotation direction, with a suction hood surrounding the tool bit in annular manner and having a workpiece engagement surface, which has a through-opening for the tool bit to pass through, whose clear width is a multiple of the diameter of the tool bit and which forms a suction duct open to the tool bit, which is limited by an outside wall, in which at least a part-zone of the outer wall is curved at least over a part of the circumference of the through-opening in a plane which runs parallel to the rotation axis of the tool bit and intersects the outer wall at two points spaced from each other.
With a known device of this type (U.S. Pat. No. 4,946,322) a cup-shaped suction hood open at the top and bottom is arranged about the rotatingly driven tool bit, said suction hood has a curved, upwardly widening outer wall, between which and a correspondingly shaped inner wall compressed air is fed, while there is a suction connection at the upper end of the suction hood. With this suction hood, the chips which are generated during the machining of the workpiece and the dust from the machining area are moved upwards and sucked away out of the inside zone of the suction hood. This requires an essentially closed top of the inner space of the suction hood, with the result that the operator's view of the machining area of the workpiece is blocked. The known suction hood is also extremely bulky and in addition operates with compressed air to effect the removal of the dust by suction.
With another known device (U.S. Pat. No. 5,031,678) the rotatingly driven tool bit is surrounded by a suction hood whose outer wall is rectilinearly inclined, at least in a part-zone, from the bottom upwards and in the direction of the rotation axis of the tool bit. A tubular suction duct joins on to this suction hood. When, with this known suction hood, chips are thrown against the inclined outer wall by the rotating tool bit, they can be reflected in the direction of the tool bit and in particular in the direction of the machining point of the workpiece. This can lead to chips and dust not being sucked out efficiently, but escaping through the groove in the workpiece created by the tool bit. In order to avoid this, a brush is therefore provided which extends into the manufactured groove and forms a barrier to the escape of chips and dust.
With another device (German Patent Application P 23 35 177) in the form of a hand-held sanding machine with rotatingly driven sanding plate, the outer wall of the dust-suction hood which surrounds the sanding area laterally is curved, with the result that sections of the outer wall which are situated above the sanding plate lie radially further inward than sections situated in the peripheral zone of the sanding plate. The suction hood is essentially completely closed at the top, with the result that the dust which has formed is retained inside the suction hood and is removed only through connected suction hoses. The curvature of the outer wall clearly serves merely to stabilise the total structure.